This invention relates to a process for the enantioselective conversion of an enantiomer mixture of 2R.sub.1, 2R.sub.2 -1,3-dioxolane-4-methanol of the formula: ##STR2## where R.sub.1 and R.sub.2 independently represent hydrogen or an optionally branched alkyl group, an aryl, or R.sub.1 and R.sub.2, together with the carbon atom to which they are attached, represent an optionally substituted carbocyclic ring, the product of said conversion being enriched in one of the enantiomers, which is achieved by subjecting this enantiomer mixture to the action of an enantioselective enzyme.
Such a process is known from EP-A-244,912. According to this published patent application, a product enriched in R-enantiomer can be obtained from an enantiomer mixture of an above-disclosed compound by subjecting such a mixture to the action of an enzyme that may originate from a great number of micro-organisms. According to the prior method it is mainly the S-enantiomer of the relevant compounds that is converted into the R-2R.sub.1, 2R.sub.2 -1,3-dioxolane-4-carboxylic acid, so that a 2R.sub.1, 2R.sub.2 -1,3-dioxolane-4-methanol enriched in R-enantiomer also remains. In said prior application it is also stated that the oxidation product, which contains an excess of R-2R.sub.1, 2R.sub.2 -1,3-dioxolane-4-carboxylic acid, can be reduced to the corresponding alcohol, in which the amount of S-2R.sub.1,2R.sub.2 -1,3-dioxolane-4-methanol is predominating.
For many applications, in particular for the use as starting compounds for the preparation of pharmaceutical compounds, it is desirable to have S-2R.sub.1, 2R.sub.2 -1,3-dioxolane-4-methanol at one's disposal. For this purpose it is desirable to be able to prepare a product enriched in S-enantiomer directly from an enantiomer mixture of 2R.sub.1, 2R.sub.2 -1,3-dioxolane-4-methanol. This can, for example, be achieved by means of an enantioselective enzymatic process.